This invention relates generally to hard disk drive assemblies for computers. More specifically, this invention relates to an automated servo track writer station which quickly and accurately places clock head and servo information on a hard disk drive assembly in accordance with computerized instructions.
In recent years, microcomputer equipment, particularly the so-called personal and desk top computers, have become extremely popular for a wide variety of business, educational and other uses. Such computers commonly include a main central processor unit having one or more memory storage disks for storage of data. In many modern computers the storage disk or disks sometimes referred to as "hard disks," are provided as part of a Winchester-type disk drive unit having the storage disks supported in a stack on a rotary spindle within a substantially sealed disk drive housing. The disks are rotatably driven in unison by a small spindle motor, and one or more electromagnetic heads on a movable actuator are displaced by a limited rotation DC motor to traverse surfaces of the rotating disks for purposes of reading and writing data. Such Winchester-type disk drive units are generally preferred in comparison with so-called floppy-type disk drives due to their higher memory storage capacities and faster operating speeds.
The actuator used in Winchester-type disk drive units resembles the traversing arm of a common phonograph, and is pivotally mounted about a shaft adjacent to an edge of the stacked storage disks. Such actuators typically include an arm assembly designed to carry the electromagnetic heads which are used to read and write data on the disk stack, and a counterbalance situated opposite the arm assembly with respect to the pivot shaft.
A coil is mounted to the counterbalance portion of the actuator to interact with a magnet assembly, for purposes of controlling the movement and positioning of the electromagnetic heads. As a current moves through the coil, it reacts with the magnet assembly to move the entire actuator assembly, comprising the actuator and the coil.
For a typical Winchester-type disk drive, data is recorded onto magnetizable surfaces or surface films on the memory storage disks in the form of data bits adapted to be encoded and decoded in binary form. The data is recorded within the confines of narrow concentric tracks defined on the disk surfaces, with track densities in the range of 500 to 1000 and more tracks per inch being relatively well know. Accordingly, the total memory storage capacity for any selected disk drive unit is directly proportional to the number of available data tracks. When the disk drive unit includes multiple storage disks, the total number of available data tracks, and thus the total memory storage capacity, is increased.
In normal operation of a Winchester-type disk drive unit, a system controller is provided for identifying the location of data which has been recorded upon the storage disks, typically through the use of directory name, file name, and/or data address information. When reading of a specific data track is desired, the system controller signals a head actuator assembly to displace the heads to the desired position for accessing the data. Alternatively, when data recording or writing is desired, the system controller signals disk drive circuitry to command the actuator assembly to displace the heads in a manner aligning one head with a vacant data track. Importantly, for accurate track seeking and head alignment therewith, detectable servo and clock information is normally prerecorded onto one or more of the memory storage disks.
In accordance with one known servo seeking and tracking system, each surface of each disk includes servo information prerecorded within radially spaced servo segments or sectors. This type of servo system, commonly known as an "embedded" servo system, provides data which is read by the operating head for purposes of seeking and tracking within a designated data track. During head traverses to seek a new specified data track, the head responds to embedded track address information within the servo sectors to identify a specified destination track. While such embedded servo systems have functioned generally satisfactorily, such systems inherently include track seek or access speed limitations due primarily to the limited sample rate at which the head can read and respond to servo information within the servo sectors. This inherent seek speed limitation is rendered more significant when relatively high track densities are used. Moreover, an embedded servo system fixes the number of available data and servo sectors in a manner which is incompatible with some types of controller interfaces.
So-called "dedicated" servo surface systems are also generally known in the art, wherein servo seeking and tracking information is pre-recorded onto one surface of a memory storage disk in a disk drive unit having multiple disks. The servo seeking and tracking information is detected by an associated servo head for purposes of displacing and aligning a group of data heads with a designated data track, or to identify track crossing during a seek/access step. Such dedicated servo surface systems are preferred in certain multiple disk microcomputer applications since they can provide an overall increased data storage capacity to the disk drive unit.
In such dedicated servo surface systems, it has been a common practice to select the lower surface of a lowermost hard disk for the application of servo data. Thus, in utilizing prior servo track writer stations this lowermost servo surface is exposed, and the hard disk assembly is inverted prior to being manually inserted into the servo track writer apparatus. Further, in prior servo track writer devices, a read/write head provided by the device is utilized to write the servo data on the dedicated servo surface, rather than the adjacent head provided by the hard disk drive assembly. It has been found, however, that errors and defects can arise in hard disk drive assemblies due to manual handling of the hard drive assembly, particularly as it is inverted and then inserted within the servo track writer. Errors may also arise when the read/write heads provided in the hard disk drive assembly do not track the data precisely as written by the independent head utilized by the servo track writer.
Accordingly, there has been a need for a novel servo track writer station which is capable of writing servo track and clock information onto a hard disk drive assembly in accordance with computerized instructions and in a manner which closely parallels actual operating parameters. Thus, an automated servo track writer station is needed which accepts the hard disk assembly and in its normal orientation, and which is capable of writing the servo data on the lowermost disk without inverting the unit. Additionally, a station is needed which minimizes manual handling of the hard disk assembly, particularly in so far as positioning of the hard disk assembly is concerned relative to operational placement within the writer station, and which isolates the hard drive assembly from vibration as the servo data is applied. Moreover, there exists a need for a servo track writer station which utilizes an actuator arm built into the hard disk assembly for purposes of writing servo data onto the dedicated disk surface, rather than a separate data arm for that purpose. The present invention fulfills these needs and provides other related advantages.